A never-before-seen "massive monster galaxy" from the early universe has been discovered by astronomers, potentially providing researchers with a "missing link" in our understanding of how large galaxies managed to form relatively shortly after the Big Bang, 13.8 billion years ago.
The newly discovered galaxy is about 12.5 billion years old. It was found by researchers from the U.S. and Australia using the Atacama Large Millimeter Array (ALMA) telescope in Chile. This telescope is designed to look at the first stars and galaxies in the universe and is able to look at light between radio and infrared—which is emitted by most objects in the universe. Unlike other telescopes, ALMA's view of this light is not obscured by the dust that normally obscures it.
Researchers led by Christina Williams, an astronomer from the University of Arizona, were carrying out observations with ALMA when they saw a faint light coming from an unknown source. "It was very mysterious because the light seemed not to be linked to any known galaxy at all," Williams said in a statement. "When I saw this galaxy was invisible at any other wavelength, I got really excited because it meant that it was probably really far away and hidden by clouds of dust."
Researchers say this light is coming from stars forming within a young galaxy that has been concealed by huge clouds of dust. Their findings are published in The Astrophysical Journal.
"We figured out that the galaxy is actually a massive monster galaxy with as many stars as our Milky Way, but brimming with activity, forming new stars at 100 times the rate of our own galaxy," study co-author Ivo Labbé, from Australia's Swinburne University of Technology, said in the statement.
Massive galaxies from the early universe pose a problem for astronomers as their existence do not fit with current theories of galaxy formation. Just after the Big Bang, the universe is thought to have expanded and cooled, eventually leading to the formation of the first atoms. About two million years later, the first stars and galaxies started to develop from clouds of gas.
Traditionally, researchers have used ultraviolet light to find the universe's first galaxies. However, this technique is blind to the massive galaxies because ultraviolet light cannot get through the clouds of dust that surround them.
As a result, these huge galaxies are underrepresented—it is thought we are missing about 90 percent of the galaxies in the universe. In August, for example, a separate team of scientists led by Tao Wang, from the University of Tokyo, Japan, found 39 massive, star forming galaxies from the early universe.
How they formed is a mystery, however.
The latest discovery may go some way to rectifying this, the team say. This is because they appear to have found a galaxy that is still forming. "Our hidden monster galaxy has precisely the right ingredients to be that missing link," Williams said.
The team now wants to know just how many massive galaxies there are in the universe—something NASA's James Webb Space Telescope (JWST) will be able to help with. This telescope, scheduled for launch in 2021, will be able to observe the early universe at longer wavelengths than other telescopes—meaning it can look further back in time to see the first stars being born.
"JWST will be able to look through the dust veil so we can learn how big these galaxies really are and how fast they are growing, to better understand why models fail in explaining them," Williams said.